EPIDERMAL GROWTH-FACTOR EXPRESSION IN HUMAN COLON AND COLON CARCINOMAS - ANTISENSE EPIDERMAL GROWTH-FACTOR RECEPTOR RNA DOWN-REGULATES THE PROLIFERATION OF HUMAN COLON-CANCER CELLS

Human colon cancer cell lines express epidermal growth factor (EGF) mR NA, secrete EGF and may respond to it via the cell-surface EGF recepto r (EGFR). Expression of these molecules in human colon and colon tumor , however, is not clear. Reverse transcription-polymerase chain reacti on (RT-PCR) analyses of RNA prepared from paired normal human colon an d colon tumor samples from IZ individuals followed by Southern blottin g analyses of the RT-PCR products revealed a major fragment of 527 bp and a minor fragment of 404 bp that hybridized to a human EGF cDNA pro be under stringent conditions. Identical results were obtained from 8 human colon cancer cell lines. Cloning and sequencing of PCR products confirmed that both fragments were from the human EGF gene; the 527-bp fragment corresponded exactly to nucleotides 2,891 to 3,417 of the hu man EGF mRNA reported by others. A deletion of 123 nucleotides (nucleo tides 3,172 to 3,294) was found in the 404-bp fragment. Immunohistoche mical studies using cryostat sections of human colon specimens showed that EGF was expressed in the human colon and that expression was rest ricted to the epithelial colonic crypt cells and epithelium-derived ca ncer cells. Since EGF and EGF-related molecules ave potent mitogens th at mediated their effect through the EGFR, we also determined the effi cacy of anti-sense EGFR RNA in circumventing the EGFR-related pathway of proliferation. Expression of anti-sense EGFR RNA, by transfection w ith an inducible anti-sense EGFR expression vector, down-regulated cel l-surface EGFR expression and proliferation of these cells and their a bility to grow in soft agar. Anti-sense EGFR RNA was found to be an an ti-proliferative agent in both relatively nonaggressive and highly agg ressive human colon cancer cells. (C) 1995 Wiley-Liss, Inc.